Transmitting and receiving data using polar codes

ABSTRACT

Methods and apparatus for transmitting and receiving data over a physical channel using a polar code are provided. The polar code defines a plurality of virtual channels within the physical channel and allocates a subset of the virtual channels for the transmission of data. Each of the subset of virtual channels for the transmission of data are mapped to respective bits of a block of data to be transmitted. The method for transmitting data: receives a block of data to be transmitted; receives additional data to be transmitted together with the block of data; selects one or more of the virtual channels which are allocated for the transmission of data as being channels for transmitting the additional data; determines a scrambling sequence based on the additional data; applies the scrambling sequence to those bits of the block of data which map onto the one or more virtual channels for transmitting the additional data to generate a scrambled version of the block of data; and transmits the scrambled version of the block of data according to the polar code, wherein error detection data is also transmitted which enables the detection of errors in the block of data. The method for receiving data: receives a scrambled version of a block of data, wherein error detection data is also received which enables the detection of errors in the block of data; identifies one or more of the virtual channels which are allocated for the transmission of data as being channels on which additional data has been transmitted, wherein the scrambled version of the block of data is formed by scrambling the bits of the block of data which were transmitted on those channels using a scrambling sequence which is based on the additional data; generates one or more hypotheses as to the scrambling sequence which has been applied to the channels on which the additional data has been transmitted; tests each of the one or more hypotheses to identify a correct hypothesis by descrambling the scrambled version of the block of data according to each hypothesis and using the error detection data to determine whether any errors are present in the descrambled block of data, wherein the correct hypothesis is one for which no errors are present in the descrambled block of data; and determines the additional data that has been transmitted based on the correct hypothesis of the scrambling sequence that has been applied to the channels on which the additional data has been transmitted.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to foreign Great Britain patentapplication Nos. GB 1707267.9, filed on May 5, 2017 and GB 1707278.6,filed on May 8, 2017, the disclosures of which are incorporated byreference in their entirety.

TECHNICAL FIELD

The present disclosure relates to the transmission and receipt of datausing Polar codes. In particular, it relates to the implicittransmission and receipt of additional data alongside a block of datawhich is transmitted or received.

BACKGROUND

Wireless communications systems, such as the third-generation (3G) ofmobile telephone standards and technology are well known. Such 3Gstandards and technology have been developed by the Third GenerationPartnership Project (3GPP). The 3rd generation of wirelesscommunications has generally been developed to support macro-cell mobilephone communications. Communication systems and networks have developedtowards a broadband and mobile system.

The 3^(rd) Generation Partnership Project has developed the so-calledLong Term Evolution (LTE) system, namely, an Evolved Universal MobileTelecommunication System Territorial Radio Access Network, (E-UTRAN),for a mobile access network where one or more macro-cells are supportedby a base station known as an eNodeB or eNB (evolved NodeB). Morerecently, LTE is evolving further towards the so-called 5G or NR (newradio) systems where one or more cells are supported by a base stationknown as a gNB (generalized NodeB).

In 3GPP there is a continual search for agreements on the implementationof new and relevant features for NR systems. The agreements are relevantto many options. One option of interest relates to the use of Polarcoding for the eMBB (enhanced Mobile Broadband) UL/DL control channels.According to this option, CRC (cyclic redundancy check) codes will beutilized either within the coded block or external in another codedblock in the case of concatenated polar codes. These CRC codes may beused to provide error detection for the blocks of data being transmittedand, in some implementations may also enable error correction.

Polar codes in 5G have been proven to achieve capacity by codeconstruction for binary erasure channel (BEC). Encoding complexity is ofO(Nlog2N) for a code block size N. Decoding complexity is of O(Nlog2N)with a successive cancellation (SC) decoder, and higher with moreadvanced decoder with better performance such as a List decoderO(LNlog2n). The implementation complexity of list decoder increases withincreasing list size, especially with large block size. Furthermore,Polar codes are not parallelizable as Turbo and LDPC, and latencyrequirements for large block-lengths are questionable. However, Polarcodes have been shown to outperform Turbo code and LDPC for short-blocklengths with no error floor for List decoder, as NR control channelrequires ultrareliability transmission.

In a communications system, encoding is generally used to improve thereliability of data transmission. The polar code is a linear block codewhich can provably achieve the Shannon capacity for a binary erasurechannel with low complexity of encoding-decoding. Conceptually, polarcodes split a physical channel up into a number of virtual channels. Thereliability of each of the virtual channels (i.e. the likelihood of abit transmitted on that channel will be successfully received) definedby a polar code differs from each other. However, generally, as thenumber of virtual channels defined by a polar code increases (e.g. as Ngoes to infinity), the reliability of each of the channels polarizes tobecome either very reliable (e.g. a perfect channel with capacity 1) orvery unreliable (e.g. a useless channel with capacity 0). The virtualchannels with the highest reliability are chosen for the transmission ofinformation bits, whilst the other virtual channels are “frozen” and arenot used for the transmission of information bits. The positions of dataand frozen bits change with the polar code construction parameter

for the same code block size. Both the encoder and the decoder mustutilize same locations of the frozen bits for a successful decodingmeaning they should know either parameter

for code construction or a pre-defined set of frozen locations which isthe outcome of the code construction.

As illustrated in FIG. 1, a polar code 120 of size N (whereby N=8 inFIG. 1) is generated by duplicating and combining n times theconstructed transform starting from duplicating and combining the basictransform 110, to give N virtual channels, where N=2^(n). It should benoted that the symbol ⊕, as used in FIG. 1, represents the exclusive OR(XOR) operation. Of these channels, the four channels having the highestreliability are indicated as being “data” channels, whilst the fourchannels having the lowest reliability are indicated as being “frozen”channels, for a code rate R=½.

Various agreements have been made in this technical area, for example:—

Agreement:

-   -   J CRC bits are provided (which may be used for error detection        and may also be used to assist decoding and potentially for        early termination)        -   J may be different in DL and UL        -   J may depend on the payload size in the UL (0 not precluded)    -   In addition, J′ assistance bits are provided in reliable        locations (which may be used to assist decoding and potentially        for early termination)    -   J+J′<=the number of bits required to satisfy the FAR target        (n_(FAR))+6        -   Working assumption:            -   For DL, n_(FAR)=16 (at least for eMBB-related DCI)            -   For UL, n_(FAR)=8 or 16 (at least for eMBB-related UCI;        -   note that this applies for UL cases with CRC)        -   J′>0        -   Working assumption: J″<=2 additional assistance bits are            provided in unreliable locations (which may be used to            assist decoding and potentially for early termination)            -   Can be revisited in RAN1#89 if significant benefit is                shown from a larger value of J″ without undue                complexity—companies are encouraged to additionally                evaluate J″=8        -   The J′ (and J″ if any) bits may be CRC and/or PC and/or hash            bits (downscope if possible)        -   Placement of the J, J′ (and J″ if any) assistance bits is            FFS after the study of early termination techniques            -   Appended?            -   Distributed?            -   evenly?            -   unevenly?                Agreements (for very small block lengths):    -   K=1 (if channel coding is applied):        -   Repetition code    -   K=2 (if channel coding is applied):        -   Simplex code    -   3<=K<=11:        -   LTE RM code            -   Note that if NR requires a codeword size N that is not                supported by the LTE RM code, then the LTE RM code will                be extended by repetition as in LTE    -   12<=K:        -   Polar code (single design for all control information sizes,            except for possible omission of CRC bits for payloads <=−22            bits)

Agreement for DCI:

-   -   Maximum mother code size of Polar code, N=2n, is:        -   Nmax,DCI=512 for downlink control information

Working Assumption for UCI:

-   -   Nmax,UCI=1024        -   Optimise code design for K up to 200            -   Also aim for code design that supports values of K up to                500 with good performance, typically using higher code                rates    -   Without prejudice to the final design, companies are encouraged        to investigate advanced code rate matching schemes until        RAN1#88bis    -   Working assumption can be revisited at RAN1#88bis if it does not        prove to be possible to generate a good code design with Nmax,        UCI=1024

Agreements:

-   -   Performance metrics (may be based on analytic derivation)        -   BLER        -   FAR (with AWGN as input to the decoder)    -   Polar codes for control channels support one of the following        alternatives:        -   Alt. 1: CRC+“basic polar” (i.e. as per above agreed            description) codes            -   1a: Longer CRC    -   e.g. (J+J′) bits CRC+basic polar        -   1b: J bit CRC            -   The J bits can be distributed        -   The CRC can be used for both error detection and error            correction    -   Alt. 2: J bits CRC+concatenated polar codes        -   e.g. J bits CRC+J′ bits CRC+basic polar;            -   J bits CRC+J′ bits distributed CRC+basic polar;            -   J bits CRC+PC bits+basic polar; (i.e. PC-Polar)            -   J bits CRC+Hash sequence+basic polar;            -   . . .        -   J bits CRC is only used for error detection

Polar coding is adopted for eMBB UL/DL control channels (LPDC wasadopted as the coding scheme for eMBB UL/DL data channels). Codingscheme(s) for URLLC and mMTC is not yet defined.

Polar code will utilize CRC, either within the coded block or externallyin another coded block in case of concatenated polar codes.

SUMMARY OF THE INVENTION

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

The present invention relates to communication systems which use Polarcodes, such as 5G/NR. The invention provides a way to implicitly signaladditional information, such as control information, using the Polarcode without increasing the coding rate. Alternatively, the inventionprovides a way to decrease the Polar coding rate without decreasing theamount of transmitted information. The code rate has a direct influenceon the block error rate (BLER) performance that improves with lower coderates.

According to a first aspect of the invention, there is provided a methodfor transmitting data over a physical channel using a polar code. Thepolar code defines a plurality of virtual channels within the physicalchannel. The polar code also allocates a subset of the virtual channelsfor the transmission of data. The polar code maps the subset of virtualchannels for the transmission of data to respective bits of a block ofdata which is to be transmitted. The method receives a block of data tobe transmitted. The method further receives additional data to betransmitted together with the block of data. The method selects one ormore of the virtual channels which are allocated for the transmission ofdata as being channels for transmitting the additional data. The methoddetermines a scrambling sequence based on the additional data. Themethod applies the scrambling sequence to those bits of the block ofdata which map onto the one or more virtual channels for transmittingthe additional data to generate a scrambled version of the block ofdata. The method transmits the scrambled version of the block of dataaccording to the polar code, wherein error detection data is alsotransmitted which enables the detection of errors in the block of data.

Since the scrambling sequence (or code) is based on the additional datawhich is to be transmitted, the application of the scrambling sequenceto the bits of the block of data which are transmitted on one or more ofthe subset of channels which are allocated for the transmission of dataenables additional data to be implicitly indicated to a receiver. Thismeans that the mother code rate of a Polar code can be effectivelydecreased, leading to better BLER performance, or equivalently higherspectral efficiency which may help a network to improve resourceutilization. Furthermore, the additional data can be implicitlytransmitted without significantly increasing the encoding or decodingcomplexity of the polar code.

The method may receive the error detection data for the block of data.The block of data that is received may comprise the error detection data(i.e. the error detection data is received as part of the block of datathat is received). However, the error detection data may be receivedseparately from the block of data. Alternatively, the method maygenerate the error detection data for the block of data.

The scrambled version of the block of data may comprise the errordetection data (i.e. the error detection may be transmitted as part ofthe scrambled version of the block of data). Alternatively, the methodmay transmit the error detection separately from the scrambled versionof the block of data.

The error detection data may comprise a cyclic redundancy check (CRC)code.

The selection of the one or more virtual channels for transmitting theadditional data may be based, at least in part, on the respectivereliabilities of the one or more virtual channels.

The method may select one or more virtual channels having a highestreliability amongst the one or more virtual channels allocated for thetransmission of data as channels for transmitting the additional data.

The method may select one or more virtual channels having a reliabilitywhich exceeds a predetermined threshold as channels for transmitting theadditional data.

By selecting the channels for transmitting the additional data based onthe respective reliabilities of the virtual channels, the method canreduce the likelihood of false positives occurring at the receiver.

The polar code block size may be smaller than the size of the receivedblock of data and the additional data may comprise those bits of thereceived block of data which are not mapped onto virtual channels by thepolar code. In other words, the method may be used to transmit a largerblock of data than the polar code block size allows by splitting thelarger block of data into a first part which fits the polar code blocksize and a second part containing the remaining data which is to beimplicitly transmitted by the method as the additional data.

The scrambling sequence may be selected from one or more distinctscrambling sequences, each distinct scrambling sequence being associatedwith a different value for the additional data. In other words, wherethere are a number of different possible values which the additionaldata may take, a distinct scrambling sequence can be provided torepresent each different possible value. For example, if the additionaldata can be any arbitrary 3-bit binary string, 8 (2³) distinctscrambling sequences may be provided, each scrambling sequence beingassociated with a different possible 3-bit binary string. As such, afirst distinct scrambling sequence may represent the binary string“000”, whilst a second distinct scrambling sequence may represent thebinary string “001” and so on.

The one or more distinct scrambling sequences comprise a scramblingsequence which is associated with an ACK in UCI and a scramblingsequence which is associated with a NACK in UCI. It will be appreciatedthat the one or more distinct scrambling sequences may comprise multipleACK/NACKs indications, for example for two TBs with 2 ACK/NACKindications accordingly, or for multiple CBGs (Code Block Groups) withmultiple ACK/NACK represented as a compressed stream.

The one or more distinct scrambling sequences may comprise scramblingsequences which are associated with SS block time index indication byPBCH.

The number of channels which are selected for transmitting theadditional data, s, may be equal to log 2K rounded up to the nextinteger value (i.e. s=[log₂K]), wherein K is the number of distinctscrambling sequences from which the scrambling sequence is selected.This provides a minimum number.

The number of channels which are selected for transmitting theadditional data, s, may be greater than log 2K rounded up to the nextinteger value (i.e. s [log₂K]), wherein K is the number of distinctscrambling sequences from which the scrambling sequence is selected.

The distinct scrambling sequences may be selected so as to maximiseHamming distances between each of the distinct scrambling sequences fora given number of virtual channels which are selected for transmittingthe additional data. The length of the scrambling sequences isdetermined by the number of virtual channels which are selected fortransmitting the additional data. There is a trade-off for selecting theright number of channels for transmitting the additional data. Whilstusing a smaller number s of virtual channels for transmitting theadditional data will mean that the reliability of the virtual channelswill be higher, using a larger number s of virtual channels fortransmitting the additional data allows greater Hamming distances toexist between each of the distinct scrambling sequences. Thefalse-positive-error rate decreases both with higher reliability ofselected channels and with greater Hamming distances between thedistinct scrambling sequences.

The method may comprise determining number of channels which areselected for transmitting the additional data to minimise the falsepositive error rate.

The scrambling sequence may comprise the additional data.

The additional data may comprise data which is already known to areceiver of the transmitted data. The additional data may comprise acell ID associated with a cell in a mobile network.

The additional data may comprise an RNTI, or a part of the RNTI.

The additional data may comprise repeated data which has previously beentransmitted. The additional data may comprise puncturing information inURLLC/eMBB multiplexing.

The polar code may be constructed according to a polar code constructionparameter ¾ which is equal to 1−R, wherein R equals the number D ofvirtual channels for the transmission of data divided by the remainingnumber of virtual channels which are not allocated to the transmissionof data. This allows the optimal re-construction of the polar code whenthe code rate is reduced relative to scenarios in which all informationis explicitly transmitted and gives D=ceil(N*R) data bits andF=floor(N*(1−R)) frozen bits, or alternatively D=floor(N*R) data bitsand F=ceil(N*(1−R)) frozen bits.

According to a second aspect of the invention, there is provided amethod for receiving data over a physical channel using a polar code.The polar code defines a plurality of virtual channels within thephysical channel. The polar code also allocates a subset of the virtualchannels for the transmission of data. The polar code maps the subset ofvirtual channels for the transmission of data to respective bits of ablock of data being transmitted. The method receives a scrambled versionof a block of data, wherein error detection data is also received whichenables the detection of errors in the block of data. The methodidentifies one or more of the virtual channels which are allocated forthe transmission of data as being channels on which additional data hasbeen transmitted, wherein the scrambled version of the block of data isformed by scrambling the bits of the block of data which weretransmitted on those channels using a scrambling sequence which is basedon the additional data. The method generates one or more hypotheses asto the scrambling sequence which has been applied to the channels onwhich the additional data has been transmitted. The method tests each ofthe one or more hypotheses to identify a correct hypothesis bydescrambling the scrambled version of the block of data according toeach hypothesis and using the error detection data to determine whetherany errors are present in the descrambled block of data, wherein thecorrect hypothesis is one for which no errors are present in thedescrambled block of data. The method determines the additional datathat has been transmitted based on the correct hypothesis of thescrambling sequence that has been applied to the channels on which theadditional data has been transmitted.

Since an error detection code is received for the block of data forwhich a scrambled version is received, the receiver can test differenthypotheses as to the scrambling sequence which was used to scramble oneor more bits of the block of data to generate the scrambled version ofthe block of data. This is because, assuming that no errors occur duringtransmission (and, of course, assuming that there are no false alarmscaused by collisions in the error detection code—however, a 16-bit CRCwill have a false alarm rate of 2⁻¹⁶ making false alarms from the errordetection code itself unlikely), only a correct hypothesis as to thescrambling sequence used to scramble the block of data will produce ablock of data which does not contain any errors when that scramblingsequence is used to descramble the scrambled version of the block ofdata. The receiver can therefore test whether a hypothesis is correct bydescrambling the data using the hypothesised scrambling code and usingthe error detection code to determine whether the descrambled block ofdata contains any errors. Since the scrambling code is determined basedon the additional data that is implicitly transmitted, the receiver canuse the correct hypothesis to determine the additional data. Whilsterrors introduced during transmission may result in a false positive fora hypothesis being tested, the operation of the polar code serves toreduce the likelihood of this happening since the channels which areallocated for the transmission of data, to which the scrambling code isapplied, are in general more reliable. Furthermore, the additional datacan be implicitly transmitted without significantly increasing theencoding or decoding complexity of the polar code.

The error detection data may be received separately from the scrambledversion of the block of data. The scrambled version of the block of datamay comprise the error detection data (i.e. the error correction datamay be received as part of the scrambled version of the block of data).

The error detection data may comprise a cyclic redundancy check (CRC)code.

The identification of the one or more virtual channels on whichadditional data has been transmitted is based, at least in part, on therespective reliabilities of the one or more virtual channels.

The identification of the one or more virtual channels on whichadditional data has been transmitted may comprise identifying one ormore virtual channels having a highest reliability amongst the one ormore virtual channels allocated for the transmission of data.

The identification of the one or more virtual channels on whichadditional data has been transmitted comprise identifying one or morevirtual channels having a reliability which exceeds a predeterminedthreshold.

Generating the one or more hypotheses as to the scrambling sequencewhich has been applied to the channels on which the additional data hasbeen transmitted may comprise generating a hypothesis for each of one ormore distinct scrambling sequences, each distinct scrambling sequencebeing associated with a different value for the additional data.

The one or more distinct scrambling sequences may comprise a scramblingsequence which is associated with an ACK in UCI and a scramblingsequence which is associated with a NACK in UCI. It will be appreciatedthat the one or more distinct scrambling sequences may comprise multipleACK/NACKs indications, for example for two TBs with 2 ACK/NACKindications accordingly, or for multiple CBGs (Code Block Groups) withmultiple ACK/NACK represented as a compressed stream.

The one or more distinct scrambling sequences comprise scramblingsequences which are associated with SS block time index indication byPBCH.

The number of channels which are identified as being channels on whichadditional data, s, has been transmitted may be equal to log 2 K roundedup to the next integer value (i.e. s [log 2K]), wherein K is the numberof distinct scrambling sequences for which hypotheses are generated.

The number of channels, s, which are identified as being channels onwhich additional data has been transmitted may be greater than log 2 Krounded up to the next integer value (i.e. s [log₂K]), wherein K is thenumber of distinct scrambling sequences for which hypotheses aregenerated.

The distinct scrambling sequences may be selected so as to maximiseHamming distances between each of the distinct scrambling sequences fora given number of virtual channels which are identified as beingchannels on which additional data has been transmitted. As discussedabove, there is a trade-off for the right number of channels on whichthe additional data is transmitted. Whilst using a smaller number s ofvirtual channels for transmitting the additional data will mean that thereliability of the virtual channels will be higher, using a largernumber s of virtual channels for transmitting the additional data allowsgreater Hamming distances to exist between each of the distinctscrambling sequences. The false-positive-error rate decreases both withhigher reliability of selected channels and with greater Hammingdistances between the distinct scrambling sequences.

The method may further comprise determining the number of channels whichare identified as being channels on which additional data has beentransmitted to minimise the false positive error rate.

Generating one or more hypotheses as to the scrambling sequence whichhas been applied to the channels on which the additional data has beentransmitted may comprise generating a prediction of the additional datawhich has been transmitted and generating a scrambling sequence whichcomprises the predicted additional data.

The prediction of the additional data is generated based on data whichalready known to the receiver. This enables the receiver to check thatthe data which the receiver already has is correct, thereby improvingrobustness and reliability of the system.

The prediction of the additional data comprises a cell ID associatedwith a cell in a mobile network. The additional data may comprise anRNTI, or a part of the RNTI.

The additional data may comprise repeated data which has previously beentransmitted and the method may further comprise determining whether therepeated data matches the data which has previously been received. Thisenables the receiver to check that data which has been receivedpreviously is correct, improving the robustness and reliability of thesystem.

The repeated data may comprise an ACK/NACK indication in UCI.

The additional data may comprise puncturing information in URLCC/eMBBmultiplexing.

The polar code may be constructed according to a polar code constructionparameter ¾ which is equal to 1−R, wherein R equals the number D ofvirtual channels for the transmission of data divided by the remainingnumber of virtual channels which are not allocated to the transmissionof data. This allows the optimal re-construction of the polar code whenthe code rate is reduced relative to scenarios in which all informationis explicitly transmitted.

According to a third aspect of the invention, there is provided anapparatus which is configured to either transmit data over a physicalchannel according to the first aspect of the invention, receive dataover a physical channel according to the second aspect of the invention,or both. For example, the apparatus may comprise a processor and atransmitter and/or receiver, wherein the processor is adapted to carryout the method of the first and/or second aspects of the invention tocause the transmitter and/or receiver to transmit and/or receive thedata over the physical channel.

The apparatus may be a base station in a mobile network. The apparatusmay be a mobile device in a mobile network.

According to a fourth aspect of the invention, there is provided amobile network comprising one or more base stations and one or moremobile devices according to the third aspect of the invention.

According to a fifth aspect of the invention, there is provided anon-transitory computer readable medium having computer readableinstructions stored thereon for execution by a processor to perform amethod according to the first and second aspects of the invention.

The non-transitory computer readable medium may comprise at least onefrom a group consisting of: a hard disk, a CD-ROM, an optical storagedevice, a magnetic storage device, a Read Only Memory, EPROM, andElectrically Erasable Programmable Read Only Memory and a Flash memory.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details, aspects and embodiments of the invention will bedescribed, by way of example only, with reference to the drawings.Elements in the figures are illustrated for simplicity and clarity andhave not necessarily been drawn to scale. Like reference numerals havebeen included in the respective drawings to ease understanding.

FIG. 1 shows the construction of a Polar code of size N;

FIG. 2 schematically illustrates a method for encoding data and a methodfor decoding data according to an embodiment of the present invention;

FIG. 3 schematically illustrates a method for DCI decoding in a specificcell ID;

FIG. 4 schematically illustrates a method for DCI decoding with RNTIextension;

FIG. 5 schematically illustrates a method for UCI decoding withACK/NACK;

FIG. 6 schematically illustrates a method for soft combining of PBCHwith implicit indication of SS time index;

FIG. 7 shows two graphs for the BLER and False-Positive Rate for fourdifferent scenarios for a polar block size of 8 with 6 bits of data;

FIG. 8 shows graphs of the BLER and False-Positive Rate for furtherscenarios which are simulated using a Polar block size of 64 with 38bits of data (22 bits of message data and 16 bits of CRC data);

FIG. 9 shows a graph of the BLER improvement provided by embodiments ofthe present invention; and

FIGS. 10-12 show simulation results.

DETAILED DESCRIPTION

Those skilled in the art will recognise and appreciate that thespecifics of the examples described are merely illustrative of someembodiments and that the teachings set forth herein are applicable in avariety of alternative settings.

A first embodiment of the present invention will now be described withreference to FIG. 2 which schematically illustrates a method 200 forencoding data and a method 250 for decoding data according to anembodiment of the present invention.

At a step 202, the method 200 for encoding data receives a block of dataor message to be transmitted. The message includes D bits which are tobe explicitly indicated. In other words, these D bits of the message ordata block map onto the virtual channels provided by the Polar code. Themessage also includes S bits which are to be implicitly indicated. Thatis to say, these S bits of the message or data block form additionaldata which will be transmitted by the method 200.

At a step 204, the method 200 constructs the polar code such that it hasD data bits to accommodate the D bits of the message which are to betransmitted. The polar code therefore also has a number F of frozen bitsgiven by F=N-D where N is the code block length. It will be appreciatedthat the Polar code need not necessarily be constructed each time datais transmitted and that a previously constructed Polar code may be usedin some embodiments.

At a step 206, the method 200 selects D′ data bit locations or virtualchannels according to the capacities or reliabilities of each of thevirtual channels.

At a step 208, the method 200 scrambles the selected D′ data bits with ascrambling sequence which is determined based on the additional datawhich is to be implicitly indicated in the transmission.

At a step 210, the method 200 encodes the scrambled data produced atstep 206 using the polar encoding.

Finally, at step 212, the method 200 transmits the encoded scrambleddata by modulating it onto a carrier.

Turning next to the method 250 for decoding data, at a step 252 themethod 250 receives the demodulated encoded scrambled data (i.e. the RXsymbols of the control channel). The demodulated encoded scrambled datamay also be considered to be a scrambled version of the block of databeing transmitted.

At a step 254, the method 250 constructs the Polar code in the samemanner as it was constructed at step 204 for the method of transmittingthe data. This is because Polar code constructed by the receiver willneed to match the construction of the Polar code used by the transmitterin order for the data to be decoded correctly. Again, it will beappreciated that the Polar code need not necessarily be reconstructedeach time the method receives data and, in some embodiments, apreviously constructed Polar code may be retrieved and used instead.

At a step 256, the method 250 selects or identifies the D′ virtualchannels (or data bit locations) which have been used to provide animplicit indication of the additional data. Again, these are identifiedaccording to the reliabilities or capacities of the virtual channelsusing the same criteria as was used at step 206 of the method 200 fortransmitting the data so as to correctly identify the channels beingused to implicitly transmit the additional data.

At a step 258, the method 250 decodes the received demodulated encodedscrambled data using the constructed Polar code.

At a step 260, the method 250 constructs and checks K hypotheses as tothe scrambling sequence that was used to scramble the bits transmittedon the D′ virtual channels. In this embodiment, the number K ofhypotheses is equal to 2^(s). This is because a unique scrambling codemay be used for implicitly indicating the S bits of additional data.

The method 250 tests the K hypotheses at steps 260 and 262 by using thehypothesised scrambling code to descramble the decoded scrambled dataand then, using a CRC code which is also received for the block of datato check whether the descrambled data is correct. In other words, themethod 250 checks whether the CRC indicates that any errors are presentin the descrambled data for each of the K hypotheses and determines thatthe correct hypothesis is the one for which the CRC passes. It will beappreciated that in other embodiments, other error detection mechanismsmay be used instead of a CRC. Having identified the correct hypothesis,the method 250 is then able to utilise the D bits of data which wereexplicitly transmitted using the Polar code as well as the S bits ofadditional data which are implicitly indicated by the scrambling codeassociated with the correct hypothesis.

A second embodiment of the invention will now be described withreference to FIG. 3 which schematically illustrates a method 300 for DCIdecoding in a specific cell ID.

In LTE, the attached CRC of DCI payload is masked with the RNTI toindicate the UE that the DCI is addressed to it, and the whole signal isscrambled with cell-ID based pseudo random sequence to reduce the intercell interference (DCI transmitted from one eNB detected as from anothereNB for same RNTI, and possibly different UEs).

In this second embodiment, rather than using a number of distinctdifferent scrambling codes which are each associated with a differentvalue of additional data, the additional data itself is used to form thescrambling code which is applied to the data bits on the D′ virtualchannels. The first four steps 252, 254, 256 and 258 of the method 300are the same as for the method of receiving data according to theprevious embodiment. However, in steps 302 and 304, only a singlehypothesis is formed and tested by the method 300. In particular, themethod 300 forms a hypothesis according to a predicted value for theadditional data which is being implicitly indicated. In this embodiment,the predicted value for the additional data is the cell ID of the DCI,which is a value which is already known to the receiver. The methodtherefore descrambles the data bits on the D′ virtual channels using ascrambling sequence which is based on the cell-ID and determines whetherthe hypothesis was correct by carrying out an XOR operation on the CRCfor the block of data and an RNTI. With this embodiment, no multiplehypotheses are needed and the DCI false-positive rate deriving frominter cell interference is reduced compared to LTE.

A third embodiment of the invention will now be described with referenceto FIG. 4 which schematically illustrates a method 400 for DCI decodingwith RNTI extension. As for the second embodiment, the additional dataitself is used to form the scrambling code which is applied to the databits on the D′ virtual channels. However, in this embodiment theadditional data which is used to generate the scrambling code is theRNTI extension. As for the previous embodiments, the first four steps252, 254, 256 and 258 of the method 400 are the same. However, thescrambling code which is used to form the hypothesis at step 402 of themethod is based on the RNTI extension that the receiver is expecting.The method 400 can then check whether this hypothesis is correct bycarrying out an XOR operation on the CRC for the block of data and theRNTI. Only a portion of the RNTI bits undergo the masking operation withthe CRC output. The remaining RNTI bits are implicitly indicated by thescrambling sequence. The CRC should pass only if the scrambling sequenceis properly set.

It will be appreciated that whilst the additional data that isimplicitly transmitted in the second and third embodiments does notprovide any new data to the receiver (since the cell ID and RNTIextension will already be known to the receiver), they allow thereceiver to carry out additional validation on the data being received,improving the robustness of the system by reducing thefalse-positive-rate deriving from intercell interference compared to LTEin the second embodiment and from other RNTIs in the third embodiment.

A fourth embodiment of the invention will now be described withreference to FIG. 5, which schematically illustrates a method 500 forUCI decoding with ACK/NACK. The first four steps 252, 254, 256 and 258of this method 500 are the same as for the previous embodiments. Theremaining steps 502 and 504 of the method 500 embodiment is similar tothe first embodiment in that more than one scrambling sequencehypothesis is formed. In this embodiment, the additional data which isimplicitly transmitted using the D′ data bits is an ACK/NACK for UCI. Adifferent scrambling sequence is used to implicitly transmit an ACK thanis used to implicitly transmit a NACK. The method 500 forms a hypothesisfor the scrambling sequence associated with an ACK and anotherhypothesis associated with a NACK and uses the CRC to test which of thetwo hypotheses is correct to determine whether an ACK or a NACK has beenreceived. In this embodiment, this implicit signalling of the ACK/NACKmay be the only way in which the ACK/NACK is transmitted.

Alternatively, this implicit signalling could be used together with the(conventional) transmission of ACK/NACK to improve itsreliability/latency (which could be very useful for URLLC). In otherwords, ACK/NACK feedback may sent explicitly, but at the same time, theD′ selected locations of data bits with highest reliability may bescrambled using a scrambling code which also implicitly conveys theACK/NACK feedback.

In a fifth embodiment of the invention, puncturing information forURLLC/eMBB multiplexing is implicitly signalled in PDCCH together withthe agreed explicit puncturing indication for URLLC/eMBB multiplexing.Repeat puncturing signalling can improve knowledge of punctured data ateMBB UE and/or provide finer info on the punctured resource. This canprovide or more of: a reduced need for ReTx; reduced explicitsignalling; and improved eMBB throughput. Optionally, an explicit signalin the DCI at the end of slot where puncturing happens can be used toinform the receiver that information about puncturing will be resentimplicitly. Then, at the next slot, on another DCI, the puncturinginformation is implicitly resent.

A sixth embodiment of the invention will now be described with referenceto FIG. 6 which schematically illustrates a method 600 for softcombining of PBCH with implicit indication of SS time index. Accordingto this embodiment, the SS time index is implicitly transmittedaccording to the invention along with the PBCH payload that isexplicitly transmitted. The PBCH signal received by a UE is dependent onthe SS block in which it was transmitted, and so the PBCH can beutilized to infer timing information at the UE. The payload is the samefor all SS blocks and can be soft combined with other received PBCHs ifthe scrambling sequence is initialised properly, as illustrated in thefigure below. The figure depicts the soft combining of two PBCHs but anynumber of PBCHs can be softly combined. The PBCH would be decoded bymeans of hypothesis testing on SS time index. This embodiment preservessoft combining of received PBCHs from consecutive SS blocks of the samebeam for performance boost, similar to that done in LTE.

In some versions of the above-described embodiments, the scramblingsequences may comprise a repetitive element or pattern. For example,scrambling sequences used to implicitly convey 3 bits of additional datacould be: 000000000 . . . , 001001001 . . . , 010010010 . . . ,011011011 . . . , 100100100 . . . , 101101101 . . . , 110110110 . . .and 111111111 . . . (i.e. using the repetitive elements “000”, “001”,“010”, “011”, “100”, “101”, “110” and “111” respectively to form thescrambling sequences). Using Reed

Solomon code to generate the scrambling sequences can further achieve amaximal Hamming distance between the scrambling sequences and can alsomake the scrambling sequences more robust.

In some embodiments of the invention, all of the virtual channels whichare allocated for the transmission of data may be selected as beingchannels for transmitting the additional data. However, in otherembodiments, it may be preferable to select a fewer number D′ ofchannels for transmitting the additional data than the total number D ofchannels allocated for the transmission of data (i.e. D′<D), especiallywhere the channels selected for transmitting the additional datacomprise a more reliable subset of the total number of channelsallocated for the transmission of data (i.e. where the averagereliability of the channels selected for transmitting the additionaldata is higher than the average reliability of all of the channelsallocated for the transmission of data). The reason for this isillustrated in FIG. 7 which shows two graphs for the BLER andFalse-Positive Rate for four different scenarios for a polar block sizeof 8 with 6 information bits being sent. FIG. 10 shows simulationresults.

The first scenario, represented by the open circle plots on these graphsrelates to a normal polar encoding using 6 data bits and 2 frozen bits,without any additional data being implicitly transmitted. The firstscenario therefore explicitly transmits all 6 bits of data.

The second scenario, represented by the cross plots on these graphsrelates to the use of the present invention to transmit the data using apolar encoding with 4 data bits and 4 frozen bits, wherein all 4 databits are scrambled with a scrambling sequence to implicitly transmit 2additional bits of data. Therefore, the second scenario explicitlytransmits 4 bits of data and implicitly transmits 2 bits of data.

The third scenario, represented by the open diamond plots on the graphsrelates to the use of the present invention to transmit the data using apolar encoding with 4 data bits and 4 frozen bits, wherein only the twodata bits with the highest capacity (or reliability) are scrambled witha scrambling sequence to implicitly transmit 2 additional bits of data.Therefore, the third scenario explicitly transmits 4 bits of data andimplicitly transmits 2 bits of data.

The fourth scenario, represented by the open square plots on the graphsrelates to the use of the present invention to transmit the data using apolar encoding with 4 data bits and 4 frozen bits, wherein the two databits with the lowest capacity (or reliability) are scrambled with ascrambling sequence to implicitly transmit 2 additional bits of data.Therefore, the fourth scenario explicitly transmits 4 bits of data andimplicitly transmits 2 bits of data.

The remaining plot shown on these graphs is not relevant to the presentinvention.

These graphs show results of tests conducted in each of the fourscenarios. In these tests, the CRC is not included and the content ofthe messages is instead checked by comparing the received bits to thetransmitted bits. As can be seen, the third scenario has a lowerfalse-positive rate compared to the second and fourth scenarios. Whilstthe false-positive rate for the third scenario is higher than for thefirst scenario, the BLER for the third scenario is lower than that ofthe first scenario.

Turning next to FIG. 8 which shows graphs of the BLER and False-PositiveRate for further scenarios which are simulated using a Polar block sizeof 64 with 38 data bits (22 bits of message data and 16 bits of CRCdata). FIG. 11 shows simulation results. The first four scenariosillustrated on FIG. 8 correspond to the four scenarios discussed abovein relation to FIG. 7. That is to say, the first scenario serves as abenchmark with all the message data bits being transmitted explicitly.The second scenario transmits 19 bits of message data explicitly andtransmits the remaining 3 bits of message data implicitly by scramblingthe data that is transmitted using 8 scrambling locations with thehighest capacity. The third scenario also only transmits 19 bits ofmessage data explicitly and transmits the remaining 3 bits of messagedata implicitly using 17 scrambling locations with highest capacity. Thefourth scenario also only transmits 19 bits of message data explicitlyand transmits the remaining 3 bits of message data using 26 scramblinglocations with the highest. Since the second, third and fourth scenariosreduce the coding rate of the polar code below that of the regular Polarcoding used in the first scenario, a fifth scenario is also included inthe graphs which includes 3 less CRC bits to provide a benchmark at thelower coding rate.

We expect a false positive rate of about ½¹⁶=1.5*10⁻⁵ deriving from theCRC, roughly multiplied by the number of tested hypotheses. From thegraphs, it can be seen that the third scenario has a lowerfalse-positive rate when compared to the regular coding with a shorterCRC (as used in the fifth scenario). This is because it takes advantageof the polar nature of the polar encoding to select locations forscrambling to implicitly convey the additional data based on thecapacity or reliability of the virtual channels.

One important observation is that it is preferable to select as manyvirtual channels for transmitting the additional data as possibleprovided that their capacity is kept close to 1 (as for the thirdscenario). By selecting more virtual channels for transmitting theadditional data, the scrambling sequences used to implicitly convey theadditional data are longer, meaning that the scrambling sequences can bemore spaced apart (i.e. have a greater Hamming distance between them)reducing the likelihood of one sequence become another through theintroduction of random errors.

Therefore, the selection of the number of channels according to thiscriterion can decrease the false-positive rate.

In order to optimize the number of channels that should be selected toimplicitly convey the additional information to decrease thefalse-positive rate, the following equations may be used to evaluate thecompeting effects of improving BLER against the degradation in the FalsePositive Rate (FPR). In these equations, the following notations areused:

N: Code block length;D: Number of channels allocated for the transmission of data;K: Number of different values of the additional data;S: Number of channels which are selected for transmitting the additionaldata (i.e., the scrambling sequence length);C: CRC (or any error correction code) length;R: Code rate;R_(ref): Code rate without implicit indication for reference;Sum{element}range: Summation of the elements within range;Mean{element}range: Average or mean value of the elements within range;andProd{element}range: Product of the elements within range.

The BLER improvement is modelled in the relevant SNR region (around BLERof ˜10-2). The FPR acts as a BLER floor for very high SNR where the BLERvalue is substantially reduced, as illustrated in FIG. 9 which shows agraph of the BLER improvement provided by embodiments of the presentinvention. The BLER improvement is given by the SNR gain in [dB] as afunction of the number of implicit bits (i.e. the number of virtualchannels allocated to the transmission of data which are selected forthe implicit transmission of the additional data).

First, the Polar code is constructed without implicit indication: Thenumber of data bits equals D+[log₂K], and the code rate equalsRref=(D+[log₂K])/N. The capacity of bits channel, Capacity_(ref), isthen calculated and the capacity ratio gives the relative capacity ofthe data bits:

CapacityRatio_(ref)=Sum{Capacity_(ref)}_(data) _(_)_(positions)/Sum{Capacity_(ref)}_(all) _(_) _(positions).

Second, the Polar code is constructed with implicit indication: Thenumber of data bits is reduced to D, and the code rate is effectivelyreduced to R=D/N. The capacity of bits channel, Capacity, is thencalculated and the capacity ratio gives the relative capacity of thedata bits:

CapacityRatio=Sum{Capacity}_(data) _(_) _(positions)/Sum{Capacity}_(all)_(_) _(positions).

Finally, the BLER improvement is given by the SNR shift in [dB]according to

BLER_improvement=10*log₁₀((1−CapacityRatio)/(1−CapacityRatio_(ref)))*R_(ref) [dB].

Equivalently this also equals to

BLER_improvement=10*log₁₀(CompCapacityRatio/CompCapacityRatio_(ref))*R_(ref) [dB],

where CompCapacityRatio_(ref)=Sum{Capacity_(ref)}_(frozen) _(_)_(positions) Sum{Capacityref}_(all) _(_) _(positions)and CompCapacityRatio=Sum{Capacity}_(frozen) _(_) _(positions)Sum{Capacity}_(all) _(_) _(positions)

The predicted FPR is given by FPR=(1+(K−1)*P)*FPR_(ref), where K is thenumber of tested hypotheses for the implicit information,FPR_(ref)=2^(−c) gives the false alarm probability for C-bits CRC lengthand P expresses the average probability of another hypothesis's sequenceto become the transmitted sequence.

To calculate P we product (multiply) the bits' probabilities, which isactually according to the Capacity of bits channel:

P=2*(((1−AvgCapacity)AvgHammingDist)*((AvgCapacity)(S−AvgHammingDist))*Prod{Capacity}data_unmasked_positions)1/D

where AvgCapacity=Mean{Capacity}_(data) _(_) _(masked) _(_) _(positions)the data masked positions are the set of S selected bits locations forscrambling, and the data un-masked positions are the complementary setin size of D−S. The average hamming distance is given by AvgHammingDisty S/sqrt [log₂K]).

Factor 2 is added to P since typically the value p1* . . . *pn)^(1/n)where all p_(i) are between 0 to 1 is a number between 0 to 1. Foruniform probabilities the average of this formula is about ½, thus withfactor 2 we get P=1, and this gives the upper bound for theFPR=K*FPR_(ref). With the proposed method this value is very close tozero in the relevant SNR region since (1−AvgCapacity) goes to zero andwe get FPR=(1+p)*FPR_(ref) where

<<(K−1).

This predicted FPR allows us to select the best S by minimizing FPR fora given number of hypotheses K, number of explicit bits D and code blocklength N: Optimal S=Argmin_(overS) {FPR}.

The signal processing functionality of the embodiments of the invention,especially the gNB and the UE may be achieved using computing systems orarchitectures known to those who are skilled in the relevant art.Computing systems such as, a desktop, laptop or notebook computer,hand-held computing device (PDA, cell phone, palmtop, etc.), mainframe,server, client, or any other type of special or general purposecomputing device as may be desirable or appropriate for a givenapplication or environment can be used. The computing system can includeone or more processors which can be implemented using a general orspecial-purpose processing engine such as, for example, amicroprocessor, microcontroller or other control module.

The computing system can also include a main memory, such as a randomaccess memory (RAM) or other dynamic memory, for storing information andinstructions to be executed by a processor.

Such a main memory also may be used for storing temporary variables orother intermediate information during execution of instructions to beexecuted by the processor. The computing system may likewise include aread only memory (ROM) or other static storage device for storing staticinformation and instructions for a processor.

The computing system may also include an information storage systemwhich may include, for example, a media drive and a removable storageinterface. The media drive may include a drive or other mechanism tosupport fixed or removable storage media, such as a hard disk drive, afloppy disk drive, a magnetic tape drive, an optical disk drive, acompact disc (CD) or digital video drive (DVD) read or write drive (R orRW), or other removable or fixed media drive. Storage media may include,for example, a hard disk, floppy disk, magnetic tape, optical disk, CDor DVD, or other fixed or removable medium that is read by and writtento by media drive. The storage media may include a computer-readablestorage medium having particular computer software or data storedtherein.

In alternative embodiments, an information storage system may includeother similar components for allowing computer programs or otherinstructions or data to be loaded into the computing system. Suchcomponents may include, for example, a removable storage unit and aninterface, such as a program cartridge and cartridge interface, aremovable memory (for example, a flash memory or other removable memorymodule) and memory slot, and other removable storage units andinterfaces that allow software and data to be transferred from theremovable storage unit to computing system.

The computing system can also include a communications interface. Such acommunications interface can be used to allow software and data to betransferred between a computing system and external devices. Examples ofcommunications interfaces can include a modem, a network interface (suchas an Ethernet or other NIC card), a communications port (such as, forexample, a universal serial bus (USB) port), a PCMCIA slot and card,etc. Software and data transferred via a communications interface are inthe form of signals which can be electronic, electromagnetic, andoptical or other signals capable of being received by a communicationsinterface medium.

In this document, the terms ‘computer program product’,‘computer-readable medium’ and the like may be used generally to referto tangible media such as, for example, a memory, storage device, orstorage unit. These and other forms of computer-readable media may storeone or more instructions for use by the processor comprising thecomputer system to cause the processor to perform specified operations.Such instructions, generally referred to as ‘computer program code’(which may be grouped in the form of computer programs or othergroupings), when executed enable the computing system to performfunctions of embodiments of the present invention. Note that the codemay directly cause a processor to perform specified operations, becompiled to do so, and/or be combined with other software, hardware,and/or firmware elements (e.g. libraries for performing standardfunctions) to do so.

In an embodiment where the elements are implemented using software, thesoftware may be stored in a computer-readable medium and loaded intocomputing system using, for example, removable storage drive. A controlmodule (in this example, software instructions or executable computerprogram code), when execute by the processor in the computer system,causes a processor to perform the functions of the invention asdescribed herein.

Furthermore, the inventive concept can be applied to any circuit forperforming signal processing functionality within a network element. Itis further envisaged that, for example, a semiconductor manufacturer mayemploy the inventive concept in a design of a stand-alone device, suchas a microcontroller of a digital signal processor (DSP), orapplication-specific integrated circuit (ASIC) and/or any othersub-system element.

It will be appreciated that, for clarity purposes, the above descriptionhas described embodiments of the invention with reference to a singleprocessing logic. However, the inventive concept may equally beimplemented by way of a plurality of different functional units andprocessors to provide the signal processing functionality. Thus,references to specific functional units are only to be seen asreferences to suitable means for providing the described functionality,rather than indicative of a strict logical or physical structure ororganisation.

Aspects of the invention may be implemented in any suitable formincluding hardware, software, firmware or any combination of these. Theinvention may optionally be implemented, at least partly, as computersoftware running on one or more data processors and/or digital signalprocessors or configurable module components such as FPGA devices. Thus,the elements and components of an embodiment of the invention may bephysically, functionally and logically implemented in any suitable way.Indeed, the functionality may be implemented in a single unit, in aplurality of units or as part of other functional units.

Although the present invention has been described in connection withsome embodiments, it is not intended to be limited to the specific formset forth herein. Rather, the scope of the present invention is limitedonly by the accompanying claims. Additionally, although a feature mayappear to be described in connection with particular embodiment, oneskilled in the art would recognize that various features of thedescribed embodiments may be combined in accordance with the invention.In the claims, the term ‘comprising’ does not exclude the presence ofother elements or steps.

Furthermore, although individually listed, a plurality of means,elements or method steps may be implemented by, for example, a singleunit or processor. Additionally, although individual features may beincluded in different claims, these may possibly be advantageouslycombined, and the inclusion in different claims does not imply that acombination of features is not feasible and/or advantageous. Also, theinclusion of a feature in one category of claims does not imply alimitation to this category, but rather indicates that the feature isequally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply anyspecific order in which the features must be performed and in particularthe order of individual steps in a method claim does not imply that thesteps must be performed in this order. Rather, the steps may beperformed in any suitable order. In addition, singular references do notexclude a plurality. Thus, references to ‘a’, ‘an’, ‘first’, ‘second’,etc. do not preclude a plurality.

Although the present invention has been described in connection withsome embodiments, it is not intended to be limited to the specific formset forth herein. Rather, the scope of the present invention is limitedonly by the accompanying claims.

Additionally, although a feature may appear to be described inconnection with particular embodiments, one skilled in the art wouldrecognise that various features of the described embodiments may becombined in accordance with the invention. In the claims, the term‘comprising’ or ‘including’ does not exclude the presence of otherelements.

Set out below and in FIG. 12 are examples of simulation results based onthe above disclosure:—

Simulated Polar block size of 64 with 38 uncoded bits, divided to 22bits for the message payload and 16 bits for CRC; 3 bits are implicitlysignalled. We expect a false positive rate of about 1/216=1.5*10−⁵deriving from the CRC, roughly multiplied by the number of testedhypotheses for worse-case.

For comparison, we simulated 38 uncoded bits with shortened CRC (only13-bits) in order to have same coding rate with regular Polar coding.

Simulated results are given below. The false-positive rate is calculatedfor the UE message, checking false positive when the CRC pass but themessage is incorrect and checking false positive when CRC pass with adifferent tested hypothesis. We observe the proposed scheme has lowerfalse-positive rate when compared to regular coding with shorter CRC,since it takes advantage of the polarity by selecting the scramblinglocations according to the capacity of bits channels.

One important observation is that it is preferable to choose as manydata bit location for scrambling as long as their capacity is kept closeto 1 (e.g. scenario 3 would be best choice); Long scrambling sequencesto convey the implicit info make it harder for one sequence to becomeanother. With such selection the false-positive rate is decreased.

Aspects of the invention are disclosed in the following numberedclauses:1. A method for transmitting data over a physical channel using a polarcode, the polar code defining a plurality of virtual channels within thephysical channel and allocating a subset of the virtual channels for thetransmission of data, each of the subset of virtual channels for thetransmission of data being mapped to respective bits of a block of datato be transmitted, the method comprising:

receiving a block of data to be transmitted;

receiving additional data to be transmitted together with the block ofdata;

selecting one or more of the virtual channels which are allocated forthe transmission of data as being channels for transmitting theadditional data;

determining a scrambling sequence based on the additional data;

applying the scrambling sequence to those bits of the block of datawhich map onto the one or more virtual channels for transmitting theadditional data to generate a scrambled version of the block of data;and

transmitting the scrambled version of the block of data according to thepolar code, wherein error detection data is also transmitted whichenables the detection of errors in the block of data.

2. The method of clause 1, wherein the method further comprisesreceiving the error detection data for the block of data.3. The method of clause 2, wherein the block of data that is receivedcomprises the error detection data.4. The method of clause 1, wherein the method further comprisesgenerating the error detection data for the block of data.5. The method of any one of the preceding clauses, wherein the scrambledversion of the block of data comprises the error detection data.6. The method of any one of clauses 1 to 4, wherein the method furthercomprises transmitting the error detection data separately from thescrambled version of the block of data.7. The method of any one of the preceding clauses, wherein the errordetection data comprises a cyclic redundancy check code.8. The method of any one of the preceding clauses, wherein the selectionof the one or more virtual channels for transmitting the additional datais based, at least in part, on the respective reliabilities of the oneor more virtual channels.9. The method of clause 8, wherein selecting the one or more virtualchannels for transmitting the additional data comprises selecting one ormore virtual channels having a highest reliability amongst the one ormore virtual channels allocated for the transmission of data.10. The method of either one of clauses 8 or 9, wherein selecting theone or more virtual channels for transmitting the additional datacomprises selecting one or more virtual channels having a reliabilitywhich exceeds a predetermined threshold.11. The method of any one of the preceding clauses, wherein the polarcode block size is smaller than the size of the received block of dataand the additional data comprises those bits of the received block ofdata which are not mapped onto virtual channels by the polar code.12. The method of any one of the preceding clauses, wherein thescrambling sequence is selected from one or more distinct scramblingsequences, each distinct scrambling sequence being associated with adifferent value for the additional data.13. The method of clause 12, wherein the one or more distinct scramblingsequences comprise a scrambling sequence which is associated with an ACKin UCI and a scrambling sequence which is associated with a NACK in UCI.14. The method of clause 12, wherein the one or more distinct scramblingsequences comprise scrambling sequences which are associated with SSblock time index indication by PBCH.15. The method of any one of clauses 12 to 14, wherein the number ofchannels which are selected for transmitting the additional data isequal to log₂ K rounded up to the next integer value, wherein K is thenumber of distinct scrambling sequences from which the scramblingsequence is selected. 16. The method of any one of clauses 12 to 14,wherein the number of channels which are selected for transmitting theadditional data is greater than log₂ K rounded up to the next integervalue, wherein K is the number of distinct scrambling sequences fromwhich the scrambling sequence is selected.17. The method of clause 16, wherein the distinct scrambling sequencesare selected so as to maximise Hamming distances between each of thedistinct scrambling sequences for a given number of virtual channelswhich are selected for transmitting the additional data.18. The method of clause 17, further comprising determining the numberof channels which are selected for transmitting the additional data tominimise the false positive error rate.19. The method of any one of clauses 1 to 11 wherein the scramblingsequence comprises the additional data.20. The method of clause 19, wherein the additional data comprises datawhich is already known to a receiver of the transmitted data.21. The method of clause 20, wherein the additional data comprises acell ID associated with a cell in a mobile network.22. The method of clause 20, wherein the additional data comprises anRNTI, or a part of the RNTI.23. The method of any one of the preceding clauses, wherein theadditional data comprises repeated data which has previously beentransmitted.24. The method of clause 23, wherein the repeated data comprises anACK/NACK indication in UCI.25. The method of any one of the preceding clauses, wherein theadditional data comprises puncturing information in URLLC/eMBBmultiplexing.26. The method of any one of the preceding clauses, wherein the polarcode is constructed according to a polar code construction parameter εwhich is equal to 1−R, wherein R equals the number D of virtual channelsfor the transmission of data divided by the remaining number of virtualchannels which are not allocated to the transmission of data.27. A method for receiving data over a physical channel using a polarcode, the polar code defining a plurality of virtual channels within thephysical channel and allocating a subset of the virtual channels for thetransmission of data, each of the subset of virtual channels for thetransmission of data being mapped to respective bits of a block of databeing transmitted, the method comprising:

receiving a scrambled version of a block of data, wherein errordetection data is also received which enables the detection of errors inthe block of data;

identifying one or more of the virtual channels which are allocated forthe transmission of data as being channels on which additional data hasbeen transmitted, wherein the scrambled version of the block of data isformed by scrambling the bits of the block of data which weretransmitted on those channels using a scrambling sequence which is basedon the additional data;

generating one or more hypotheses as to the scrambling sequence whichhas been applied to the channels on which the additional data has beentransmitted;

testing each of the one or more hypotheses to identify a correcthypothesis by descrambling the scrambled version of the block of dataaccording to each hypothesis and using the error detection data todetermine whether any errors are present in the descrambled block ofdata, wherein the correct hypothesis is one for which no errors arepresent in the descrambled block of data; and

determining the additional data that has been transmitted based on thecorrect hypothesis of the scrambling sequence that has been applied tothe channels on which the additional data has been transmitted.

28. The method of clause 27, wherein the error detection data isreceived separately from the scrambled version of the block of data.29. The method of clause 27, wherein the scrambled version of the blockof data comprises the error detection data.30. The method of any one of clauses 27 to 29, wherein the errordetection data comprises a cyclic redundancy check code.31. The method of any one of clauses 27 to 30, wherein theidentification of the one or more virtual channels on which additionaldata has been transmitted is based, at least in part, on the respectivereliabilities of the one or more virtual channels.32. The method of clause 31, wherein the identification of the one ormore virtual channels on which additional data has been transmittedcomprises identifying one or more virtual channels having a highestreliability amongst the one or more virtual channels allocated for thetransmission of data.33. The method of clause 32, wherein the identification of the one ormore virtual channels on which additional data has been transmittedcomprises identifying one or more virtual channels having a reliabilitywhich exceeds a predetermined threshold.34. The method of any one of clauses 27 to 33, wherein generating theone or more hypotheses as to the scrambling sequence which has beenapplied to the channels on which the additional data has beentransmitted comprises generating a hypotheses for each of one or moredistinct scrambling sequences, each distinct scrambling sequence beingassociated with a different value for the additional data.35. The method of clause 34, wherein the one or more distinct scramblingsequences comprise a scrambling sequence which is associated with an ACKin UCI and a scrambling sequence which is associate with a NACK in UCI.36. The method of clause 34, wherein the one or more distinct scramblingsequences comprise scrambling sequences which are associated with SSblock time index indication by PBCH.37. The method of any one of clauses 34 to 36, wherein the number ofchannels which are identified as being channels on which additional datahas been transmitted is equal to log₂ K rounded up to the next integervalue, wherein K is the number of distinct scrambling sequences forwhich hypotheses are generated.38. The method of any one of clauses 34 to 36, wherein the number ofchannels which are identified as being channels on which additional datahas been transmitted is greater than log₂ K rounded up to the nextinteger value, wherein K is the number of distinct scrambling sequencesfor which hypotheses are generated.39. The method of clause 38, wherein the distinct scrambling sequencesare selected so as to maximise Hamming distances between each of thedistinct scrambling sequences for a given number of virtual channelswhich are identified as being channels on which additional data has beentransmitted.40. The method of clause 39, further comprising determining the numberof channels which are identified as being channels on which additionaldata has been transmitted to minimise the false positive error rate.41. The method of any one of clauses 27 to 35, wherein generating one ormore hypotheses as to the scrambling sequence which has been applied tothe channels on which the additional data has been transmitted comprisesgenerating a prediction of the additional data which has beentransmitted and generating a scrambling sequence which comprises thepredicted additional data.42. The method of clause 41, wherein the prediction of the additionaldata is generated based on data which already known to the receiver.43. The method of clause 42, wherein the prediction of the additionaldata comprises a cell ID associated with a cell in a mobile network.44. The method of clause 42, wherein the additional data comprises anRNTI, or a part of the RNTI.45. The method of any one of clauses 27 to 44, wherein the additionaldata comprises repeated data which has previously been transmitted andthe method further comprises determining whether the repeated datamatches the data which has previously been received.46. The method of clause 45, wherein the repeated data comprises anACK/NACK indication in UCI.47. The method of any one of clauses 27 to 46, wherein the additionaldata comprises puncturing information in URLCC/eMBB multiplexing.48. The method of any one of clauses 27 to 47, wherein the polar code isconstructed according to a polar code construction parameter ε which isequal to 1−R, wherein R equals the number D of virtual channels for thetransmission of data divided by the remaining number of virtual channelswhich are not allocated to the transmission of data.49. An apparatus which is configured to either transmit data over aphysical channel according to the method of any one of clauses 1 to 26,receive data over a physical channel according to the method of any oneof clauses 27 to 48, or both.50. The apparatus of clause 49, wherein the apparatus is a base stationin a mobile network.51. The apparatus of clause 49, wherein the apparatus is a mobile devicein a mobile network.52. A mobile network comprising one or more base stations according toclause 50 and one or more mobile devices according to clause 51.53. A non-transitory computer readable medium having computer readableinstructions stored thereon for execution by a processor to perform themethod according to any one of clauses 1 to 48.

1. A method for transmitting data over a physical channel using a polar code, the polar code defining a plurality of virtual channels within the physical channel and allocating a subset of the virtual channels for the transmission of data, each of the subset of virtual channels for the transmission of data being mapped to respective bits of a block of data to be transmitted, the method comprising: receiving a block of data to be transmitted; receiving additional data to be transmitted together with the block of data; selecting one or more, but not all, of the virtual channels which are allocated for the transmission of data as being channels for transmitting the additional data; determining a scrambling sequence based on the additional data; applying the scrambling sequence to those bits of the block of data which map onto the one or more virtual channels selected for transmitting the additional data to generate a scrambled version of the block of data; and transmitting the scrambled version of the block of data according to the polar code, wherein error detection data is also transmitted which enables the detection of errors in the block of data.
 2. The method of claim 1, wherein the method further comprises receiving the error detection data for the block of data.
 3. The method of claim 2, wherein the block of data that is received comprises the error detection data.
 4. The method of claim 1, wherein the method further comprises generating the error detection data for the block of data.
 5. The method of claim 1, wherein the error detection data comprises a cyclic redundancy check code.
 6. The method claim 1, wherein the selection of the one or more virtual channels for transmitting the additional data is based, at least in part, on the respective reliabilities of the one or more virtual channels.
 7. The method of claim 6, wherein selecting the one or more virtual channels for transmitting the additional data comprises selecting one or more virtual channels having a highest reliability amongst the one or more virtual channels allocated for the transmission of data.
 8. The method of claim 1, wherein the scrambling sequence is selected from one or more distinct scrambling sequences, each distinct scrambling sequence being associated with a different value for the additional data.
 9. The method of claim 8, wherein the scrambling is associated with SS block time index indication by PBCH.
 10. The method of claim 1, wherein the scrambling sequence comprises the additional data.
 11. The method of claim 10, wherein the additional data comprises data which is already known to a receiver of the transmitted data, and optionally the additional data comprises a cell ID associated with a cell in a mobile network.
 12. A method for receiving data over a physical channel using a polar code, the polar code defining a plurality of virtual channels within the physical channel and allocating a subset of the virtual channels for the transmission of data, each of the subset of virtual channels for the transmission of data being mapped to respective bits of a block of data being transmitted, the method comprising: receiving a scrambled version of a block of data, wherein error detection data is also received which enables the detection of errors in the block of data; identifying one or more, but not all, of the virtual channels which are allocated for the transmission of data as being channels on which additional data has been transmitted, wherein the scrambled version of the block of data is formed by scrambling the bits of the block of data which were transmitted on those channels using a scrambling sequence which is based on the additional data; generating one or more hypotheses as to the scrambling sequence which has been applied to the channels on which the additional data has been transmitted; and testing each of the one or more hypotheses to identify a correct hypothesis by descrambling the scrambled version of the block of data according to each hypothesis and using the error detection data to determine whether any errors are present in the descrambled block of data, wherein the correct hypothesis is one for which no errors are present in the descrambled block of data.
 13. The method of claim 12, wherein the error detection data is received separately from the scrambled version of the block of data.
 14. The method of claim 12, wherein the scrambled version of the block of data comprises the error detection data.
 15. The method of claim 12, wherein the error detection data comprises a cyclic redundancy check code.
 16. The method of claim 12, wherein generating the one or more hypotheses as to the scrambling sequence which has been applied to the channels on which the additional data has been transmitted comprises generating a hypotheses for each of one or more distinct scrambling sequences, each distinct scrambling sequence being associated with a different value for the additional data.
 17. The method of claim 16, wherein the scrambling sequence is associated with SS block time index indication by PBCH.
 18. The method of claim 12, wherein generating one or more hypotheses as to the scrambling sequence which has been applied to the channels on which the additional data has been transmitted comprises generating a prediction of the additional data which has been transmitted and generating a scrambling sequence which comprises the predicted additional data.
 19. The method of claim 18, wherein the prediction of the additional data is generated based on data which already known to the receiver, or the prediction of the additional data comprises a cell ID associated with a cell in a mobile network.
 20. The method of claim 12, further comprising determining the additional data that has been transmitted based on the correct hypothesis of the scrambling sequence that has been applied to the channels on which the additional data has been transmitted. 